Effect of Supporting Background Electrolytes on the Nanostructure Morphologies and Electrochemical Behaviors of Electrodeposited Gold Nanoparticles on Glassy Carbon Electrode Surfaces

Abstract

Electrodeposition is an electrochemical method employed to deposit stable and robust gold nanoparticles (AuNPs) on electrode surfaces for creating chemically modified electrodes (CMEs). The use of several electrodeposition techniques with different experimental parameters allow in obtaining various surface morphologies of AuNPs deposited on the electrode surface. By considering the electrodeposition of AuNPs in various background electrolytes could play an important strategy in finding the most suitable formation of the electrodeposited AuNP films on the electrode surface. This is because different electrode roughnesses can have different effects on the electrochemical activities of the modified electrodes. Thus, in this study, the electrodeposition of AuNPs onto the glassy carbon (GC) electrode surfaces in various aqueous neutral and acidic electrolytes was achieved by using the cyclic voltammetry (CV) technique with no adjustable CV parameters. Then, surface morphologies and electrochemical activities of the electrodeposited AuNPs were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), CV, and electrochemical impedance spectroscopy (EIS). The obtained SEM and 3D-AFM images show that AuNPs deposited at the GC electrode prepared in NaNO3 solution form a significantly better, uniform, and homogeneous electrodeposited AuNP film on the GC electrode surface with nanoparticle sizes ranging from ∼36 to 60 nm. Meanwhile, from the electrochemical performances of the AuNP-modified GC electrodes, characterized by using a mixture of ferricyanide and ferrocyanide ions [Fe­(CN6)3–/4–], there is no significant difference observed in the case of charge-transfer resistances (R ct) and heterogeneous electron-transfer rate constants (k o), although there are differences in the surface morphologies of the electrodeposited AuNP films. Remarkably, the R ct values of the AuNP-modified GC electrodes are lower than those of the bare GC electrode by 18-fold, as the R ct values were found to be ∼6 Ω (p < 0.001, n = 3). This has resulted in obtaining k o values of AuNP-modified GC electrodes between the magnitude of 10–2 and 10–3 cm s–1, giving a faster electron-transfer rate than that of the bare GC electrode (10–4 cm s–1). This study confirms that using an appropriate supporting background electrolyte plays a critical role in preparing electrodeposited AuNP films. This approach could lead to nanostructures with a more densely, uniformly, and homogeneously electrodeposited AuNP film on the electrode surfaces, albeit utilizing an easy and simple preparation method.

Deciphering the Molecular Mechanism of Substrate-Induced Assembly of Gold Nanocube Arrays toward an Accelerated Electrocatalytic Effect Employing Heterogeneous Diffusion Field Confinement

“…Drop-casting AuNCs on the GC surface notably increased the peak redox currents compared with that of the pristine GC electrode (Figure B). A similar observation was previously made in the case of decoration with gold nanoparticles and was connected to the increase in electrical conductivity . Furthermore, the effective increase in the electron transfer kinetics was confirmed by tracking the decrease in anodic–cathodic peak separation (Δ E p ) from 84 to 71 mV after AuNC deposition.…”

“…As a result, in the SECM experiment, a reduction signal from both the AuNC and the substrate is observed only for the GC template. Notably, the enhancement of the electrochemical performance by AuNC/GC was previously discussed to be solely contributed by the good electrical conductivity of the electrode surface . Our findings also explain the increasing Fe­(CN) 6 3– reduction rate constant k 0 , which is noted only in the case of AuNC/GC.…”

“…A similar observation was previously made in the case of decoration with gold nanoparticles and was connected to the increase in electrical conductivity. 56 Furthermore, the effective increase in the electron transfer kinetics was confirmed by tracking the decrease in anodic− cathodic peak separation (ΔE p ) from 84 to 71 mV after AuNC deposition. A similar feature was observed for Au, but not for ITO, where ΔE p remained around 155 mV, suggesting a significantly higher irreversibility of the electron transfer.…”

Deciphering the molecular mechanism of substrate-induced assembling of gold nanocube arrays toward accelerated electrocatalytic effect employing heterogeneous diffusion fields confinement

“…2B). A similar observation was previously made in the case of decoration with gold nanoparticles and was connected to the increase in electrical conductivity 53 . Furthermore, the effective increase of the electron transfer kinetics was confirmed by tracking the decrease in anodic-tocathodic peak separation (ΔEp) from 84 to 71 mV after AuNC deposition.…”

“…As a result, in the SECM experiment, a reduction signal from both the AuNC and substrate is observed only for the GC template. Notably, the electrochemical performance enhancement by AuNC/GC was previously discussed to be solely contributed by good electrical conductivity of the electrode surface 53 . Our findings also explain the rising of Fe(CN)6 3reduction rate constant k 0 , which is noted only in case of AuNC/GC.…”